Journal of Drive and Control (드라이브 ㆍ 컨트롤)

The Korean Society for Fluid Power and Construction Equipment (유공압건설기계학회)
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Robust Internal-loop Compensation of Pump Velocity Controller for Precise Force Control of an Electro-hydrostatic Actuator

EHA의 정밀 힘제어를 위한 펌프 속도 제어기의 강인 내부루프 보상

  • Kim, Jong-Hyeok (Aerospace & Mechanical Engineering, Graduate School, Korea Aerospace University) ;
  • Hong, Yeh-Sun (Aerospace & Mechanical Engineering, Korea Aerospace University)
  • Received : 2018.09.13
  • Accepted : 2018.10.31
  • Published : 2018.12.01
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Abstract

Force-controlled electro-hydrostatic actuators have to exhibit high backdrivability, to quickly compensate for force control errors caused by externally disturbed rod movement. To obtain high backdrivability, the servomotor for driving the hydraulic pump, should rotate exactly to such a revolution to compensate for force control errors, compressing or decompressing cylinder chambers. In this study, we proposed a modified velocity control structure, including a robust internal-loop compensator (RIC)-based velocity controller, for the servomotor to improve backdrivability of a force-controlled EHA. Performance improvement was confirmed experimentally, wherein sinusoidal velocity disturbance was applied to the force-controlled EHA, with constant reference input. Its dynamic force control errors reduced effectively, with the proposed control scheme, compared to test results with a conventional motordriver, for motor velocity control.

Keywords

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Fig. 1 Configuration of force-controlled EHA

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Fig. 2 Conventional velocity control scheme of a servomotor

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Fig. 3 Modified structure of motor velocity controller

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Fig. 4 RIC-based motor velocity control scheme

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Fig. 5 Configuration of backdrivability test system

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Fig. 6 Experimental apparatus

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Fig. 7 Test results of motor velocity control without load

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Fig. 8 Cylinder displacement for backdrivability test

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Fig. 9 Test results with a reference force of 0N

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Fig. 10 Test results with a reference force of 500N

Table 1 Specifications of experimental apparatus

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